The carol service, held at Westminster Abbey in December, is being broadcast on ITV on Christmas Eve at 7.30pm, having been switched from the BBC in the fallout over a BBC Two documentary about the Duke of Cambridge and the Duke of Sussex.
ITV have shared the first clip of the Together At Christmas service, which teases the festive performances, readings and carols.
The video opens with the Duke and Duchess of Cambridge arriving at the Abbey as a voiceover by actor James McAvoy says: “Join her royal highness, the Duchess of Cambridge, with special guests and music performances.”
Kate, wearing a red and white Christmas jumper, adds: “I am so excited to be hosting Together At Christmas here at Westminster Abbey.”
TV presenter Kate Garraway speaks during the service, after her husband Derek Draper spent a year in hospital with coronavirus.
Singers Tom Walker, Ellie Goulding and Leona Lewis also perform.
The Christmas service was also attended by England footballer Jordan Henderson, comic Jason Manford, Zara and Mike Tindall, Princess Beatrice and her husband Edoardo Mapelli Mozzi, Princess Eugenie and the Countess of Wessex.
Kate’s parents Carole and Michael Middleton, her sister Pippa Matthews and brother James Middleton and his wife Alizee also supported her at the event.
The duchess organised the concert to reflect on the challenges of the pandemic and pay tribute to the people and organisations who have supported communities through the Covid-19 crisis.
The congregation was filled with 1,200 unsung Covid heroes, and the duchess welcomed familiar faces including Mila Sneddon, six, who charmed the duchess after bravely coping with leukaemia during the pandemic.
The youngster, from Falkirk, in Scotland, was a guest of honour after meeting the duchess through the Hold Still photo project. She sat behind Kate and the other members of the royal family, and also gave a short reading during the hour-long ceremony.
Royal Carols: Together At Christmas will air on Christmas Eve at 7.30pm on ITV and ITV Hub.